1. Field of the Invention
The present invention relates to the treatment of eating and gastrointestinal disorders, and in particular to the treatment of eating and gastrointestinal disorders through transcutaneous electrical nerve stimulation (“TENS”) of the sympathetic nerve pathways innervating the stomach.
2. Description of the Related Art
According to the American Medical Association, obesity is reaching epidemic proportions, affecting over 30% of American adults, or almost 70 million people. And that percentage is climbing. In addition to the health risks presented by obesity itself, obesity increases the likelihood of a wide range of significant co-morbid health risks including cardiovascular complications (such as hypertension and hyperlipidemia), diabetes, gallbladder disease, cancer, polycystic ovary disease, pregnancy-related problems, arthritis-related problems and other orthopedic complications caused by stress on body joints.
Obesity may have several causes. Genetic, environmental and psychological factors are all believed to play a role in obesity. The mechanism for weight gain includes impaired metabolism of adipose tissue, physical inactivity (due to lifestyle or other illness), and uncontrolled appetite. Some illnesses, such as hypothyroidism, Cushing's disease and depression can also lead to obesity partly through hormonal effects, and partly through changes in appetite and lifestyle.
Regarding hormonal effects on obesity, the control of thyroid hormone secretion and adrenal gland secretion is at the level of the hypothalamus and pituitary regions of the brain. The hypothalamus secretes thyroid releasing factor which leads to release of thyroid stimulation hormone from the pituitary gland leading to increases in thyroid hormone production and release from the thyroid gland. In a similar fashion Corticotrophin releasing factor released from the hypothalamus leads to release of adrenocorticotrophic hormone that causes increased cortisol secretion from the adrenal glands causing Cushing's disease.
Obesity may further be caused by certain drugs, such as steroids and some antidepressants and these effects are also thought to occur in the appetite centers in the brain. Obesity is a common feature of neurologic diseases that appear to affect the appetite control center in the hypothalamic, pituitary, and brain stem regions of the brain. Kline-Levine syndrome, sarcoidosis of the hypothalamus, tumors of the hypothalamus, for example, are associated with massive obesity.
When diet therapy proves ineffective, morbid obesity is often treated through bariatric surgery. A pair of common bariatric surgical procedures are adjustable gastric banding and vertical banded gastroplasty (VBG). In these procedures, a band is surgically placed around the upper part of the stomach creating a small pouch. The pouch fills quickly when eating or drinking giving the patient the sensation of satiety. Another popular treatment is the Roux-en-Y gastric bypass, in which a small stomach pouch is created, and a section of the small intestine is attached to the pouch to allow food to bypass the lower stomach, the duodenum, and the first portion of the jejunum. This bypass reduces the amount of calories and nutrients the body absorbs. It is also known to surgically place a balloon within the stomach which then may be inflated with saline to induce a feeling of satiety. A still further surgical treatment for obesity is a gastric pacemaker, which is surgically implanted into the wall of the stomach. Electrical impulses from the device stimulate nerves to reduce appetite. Gastric pacemakers have also been known as a treatment for gastroparesis, a condition where peristalsis is impaired due to the slowing or stopping of the natural gastric slow wave pacemaker activity of the enteric nerve plexus innervating the stomach. Though there are many causes, gastroparesis often results from diabetes or damage to the vagus nerve(s).
Each of the above-described bariatric procedures has associated risks. A significant concern with banded surgeries is a high incidence of complications, such as bleeding and/or obstruction. Though generally better tolerated than banded procedures, the Roux-en-Y gastric bypass still results in significant complications, such as vitamin and mineral deficiencies, and may lead to osteoporosis in the long-term.
Additionally, while any surgical procedure involves risks, surgical procedures on obese patients present significantly higher risks of complications and death. The obesity itself as well as any co-morbid conditions associated with obesity makes it difficult to administer anesthesia in proper doses. The surgical wounds often do not heal properly. And obese patients face a higher risk of complications after surgery, such as deep venous thrombosis.
Severe weight loss and abnormal loss of appetite is an equally serious condition that can lead to suffering and death. The most common example is anorexia nervosa, a condition that classically affects young women and is associated with pathologic alterations of hypothalamic and pituitary gland function. Severe anorexia can also occur in bowel conditions that cause early satiety (a feeling of fullness) or pain on eating. While anorexia is treatable with behavioral modifications, most patients require psychotropic drugs that appear effective in increasing appetite.
Transcutaneous electrical nerve stimulation, or TENS, uses a small electrical device to deliver electrical impulses through the skin via electrode pads affixed to the skin. It is typically used to reduce pain, but TENS has also been used to relieve stiffness and improve mobility. TENS is thought to work by at least one of two physiological processes. The first is by the so-called gate control theory of pain. According to this theory, small diameter nerve fibers carry pain stimuli through a theoretical “gate mechanism” but larger diameter nerve fibers can inhibit the transmission of pain stimuli by the smaller nerves, in effect blocking or closing this theoretical gate. It is believed that by stimulating the large nerve fibers through TENS, the gate can be closed to block the pain. Under the second theory, TENS is believed to stimulate the production of endorphins, which are natural pain relieving hormones produced by the body.